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In this experiment, students are given a fanciful application of the standard addition method to evaluate the approximate quantity of the shell component in a sample of sand collected on the Lido di Venezia seashore. Several diffuse reflectance infrared Fourier transform (DRIFT) spectra are recorded from a sand sample before and after addition of known amounts of powdered shell. A peak, characteristic of shells, is selected and its normalized intensity is plotted against the percentage of added shell powder. By means of a linear regression, the initial concentration of the component from shells of the sand is estimated. The proposed approach, based on a method for mixtures and impurity determination, requires students to perform DRIFT spectroscopic measurements of a powdery material and, depending on the starting material, offers the chance to verify the influence of grain size on spectral features. Well-known distortion effects on peak intensities and line shapes due to sample inhomogeneities that usually make DRIFTS a poor technique for quantitative measurements are circumvented by asking students to follow a strict procedure for sample preparation. The proposed experiment can be carried out in one or two lab periods depending whether students are asked to prepare starting powders or determine the optical response curve and is designed for either undergraduate or graduate students.

The Fourier transform infrared spectrum of CH2--~-CHF has been investigated in the v7 band region around 115 5 cm -1 at a resolution of about 0"002 cm-1. This fundamental of symmetry species A' yields an a/b hybrid band with a prevalent contribution of the a-type component. The band is affected by first-order b-Coriolis resonance with the v9 + v12 combination, and the interactions are markedly stronger for the K'a = 11 and 12 levels; local perturbations with crossings due to higher-order a-and b-Coriolis resonances have also been observed. The rovibrational analysis led to the identification of more than 2900 lines of v7 with J ~< 64 and Ka ~< 18, while no features were detected for the v9 + v12 band. Using Watson's A-reduction Hamiltonian in the I" representation, the present ground state combination differences combined with available microwave data led to improved sextic distortion terms for the ground state. Of the assigned lines, 2329 free of major resonance contribution provided excited state constants for the v 7 band. Furthermore, from the perturbation effects near the crossings, some parameters for the v 9 + v12 combination have been determined.

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The experiment outlined in this paper exploits basic multivariate analysis (MVA) to identify in a number of diffuse reflectance infrared Fourier transform (DRIFT) spectra those corresponding to samples with similar compositions.\ud The object of this work is the spectroscopic study of sand samples from different locations, whose DRIFT spectra exhibit features reflecting their composition. MVA has been shown to effectively sort subsets of homogeneous specimens collected in the same area, as well as pointing out similarities in composition among sands of different origin.\ud This experiment is designed for graduate students and provides a practical application of both solid state spectroscopy and chemometrics. It is helpful to students already acquainted with MVA and willing to develop some spectroscopic skills or merely aiming to collect some data sets to work with. Conversely, the technique can be used by students familiar with spectroscopy who wish to investigate multivariate exploratory data analysis. \ud The spectra can also illustrate a discussion of the spectroscopy of minerals (ad-hoc flow-charts for the identification of the main constituents of sands through their spectral features are proposed)